This invention relates to power amplifiers and amplifying methods, and more particularly to high-efficiency power amplifiers and related methods
Power amplifiers are widely used in communication systems, for example in radiotelephone base stations and radiotelephones. In radiotelephone communication systems, power amplifiers typically amplify high frequency signals for transmission.
A major consideration in the design of power amplifiers is the efficiency thereof. High efficiency is generally desirable so as to reduce the amount of power that is dissipated as heat. Moreover, in many applications, such as in satellites and portable radiotelephones, the amount of power that is available may be limited. An increase in efficiency in the power amplifier therefore may be desirable, in order to allow an increase the operational time or capacity for the satellite or portable radiotelephone.
In U.S. Pat. No. 2,210,028 to Doherty (August 1940), an arrangement of two vacuum tube power amplifiers coupled by a single quarter wave line is described. A semiconductor version of the Doherty amplifier is described in a more recent U.S. Pat. No. 5,420,541 entitled xe2x80x9cMicrowave Doherty Amplifierxe2x80x9d, to Upton et al. In Proc. IRE, Vol. 23 No. 11 (1935), pages 1370-1392, entitled xe2x80x9cHigh Power Outphasing Modulationxe2x80x9d, Chireix describes producing a transmitter giving a modulated amplitude output signal by combining two constant output amplitude amplifiers with a variable phase difference so that their outputs can be varied in relative phase from additive to subtractive. In U.S. Pat. Nos. 5,568,088; 5,574,967; 5,631,604; and 5,638,024 to Dent, all entitled xe2x80x9cWaste Energy Control and Management in Power Amplifiersxe2x80x9d, various arrangements of coupled power amplifiers are disclosed in which a varying amplitude signal may be produced using constant amplitude power amplifiers. In applicant""s 1964 graduate thesis project, an amplifier was built and reported in which the value of Vcc was selected to be either Vcc or 0.7 Vcc based on whether the desired output amplitude was greater or less than 0.7 Vcc. Finally, in the 1960s, many so-called xe2x80x9cclass-Dxe2x80x9d or pulse-width modulation amplifiers were proposed and manufactured.
Bidirectional Direct Current (DC) power conversion circuits and methods according to embodiments of the invention transfer DC power in a forward direction from a first terminal at a first voltage to a second terminal at a second voltage, wherein the first voltage is higher than the second voltage relative to a common voltage at a common terminal, and in a reverse direction from the second terminal at the second voltage to the first terminal at the first voltage. Bidirectional DC power conversion circuits and methods according to embodiments of the present invention use an inductor having first and second inductor ends, a first switch that is connected between the first terminal and the first inductor end to define a node therebetween, and a second switch that is connected between the node and the common terminal, wherein the second inductor end is connected to the second terminal. In these embodiments, a switch controller/method is configured to simultaneously close the first switch and open the second switch, to simultaneously open the first switch and close the second switch, and to maintain the first switch closed and the second switch open for a percentage of time that approximates a ratio of the second voltage to the first voltage. Power is thereby transferred from the second terminal to the first terminal when current flows from the first terminal to the second terminal, and power is thereby transferred from the first terminal to the second terminal when current flows from the second terminal to the first terminal.